1. Field of the Invention
This invention relates to a tracing device for mandibular movement and a tracing method therefor.
More particularly, this invention relates to a tracing device for mandibular movement and a tracing method therefor, which can be carried out easily in a dental clinic to provide a centric jaw relation record and an eccentric movement record, even in the case of a patient whose oral cavity is either in a dentulous state or in an edentulous state.
This invention relates to a tracing device for mandibular movement and a tracing method therefor, which makes possible a centric jaw relation record and an eccentric movement record without requiring the elevation of the occlusal vertical dimension, especially even when the patient retains some healthy teeth.
2. Description of the Prior Art
Conventionally, it is already known that the record of jaw relation and mandibular movement in dental clinics have been carried out mainly by one of the following methods:
a. checkbite method,
b. panthograph method, and
c. chewing method.
Moreover, it is publicly known that many devices and methods to carry out the above mentioned methods concretely.
Among them, the checkbite method which utilizes the apex if a traced figure of a mandibular movement (so called Gothic arch) as a centric relation of a mandible and a point on a border moving path as a jaw position at an eccentric mandibular movement, and then fixes and records said jaw relations by means of the Christensen phenomenon is most widely used. It is publicly known that there are many kinds of devices to carry out the method as classified as follows:
(1) intraoral mandibular movement tracing devices, for example, Hesse, Sharry, Gysi, Messerman, Swenson, Gerber, Mc. Grane, Sosin, Okino and Oba, Nihon Dental University type, Bernea, Andresen, Bimeter, Granger and the like;
(2) extraoral mandibular movement tracing devices, for example, Gysi, Occlusolator, Okino and the like;
(3) intraoral and extraoral mandibular movement tracing devices which can be used cooperatively are, for example, Bimeter, Stansvery, Robinson, Hanau, Lott, Sears Trivet and the like.
However, originally most of the above mentioned devices have been developed to trace the mandibular movement of edentulous patients. Therefore, they have had many difficulties in practical use in clinics, when those devices were used on dentulous patients since every device could not be used without some elevation of the occlusion. They also had common defects in that the centric relation and/or the border moving path were recorded inaccurately.
Moreover, in addition to the above defects, the intraoral tracing devices had the following defects.
(1) It was difficult to observe the tracing at the centric jaw relation and the eccentric movement, and when the checkbite was taken, it was difficult to confirm whether a jaw relation was properly secured to a predetermined centric relation or an eccentric relation.
(2) The traced figure of the mandibular movement was relatively small and it was difficult to distinguish clearly the apex of the Gothic arch.
(3) Because the tracing pin served as a supporting nail (called support stud hereinafter) and as a tracing pin simultaneously, traced lines were relatively large and inaccurate. And also dependent on the position of the tracing pin which displaced the record base on which a tracing device was connected.
(4) As a result of the existence of the tracing device, patients often felt a sense of discomfort as their tongue was pressed by the tracing device interrupting the smooth movement of the mandible.
(5) In determining the settling position of the jaw relation, the devices necessitated repeated attachments and detachments in the course of operation, and there was a danger that resultant records could include errors.